Corn plant named `Sun Star`

ABSTRACT

A new and distinct corn plant which is the product of a cross between diploid Tripsacum dactyloides and Zea diploperennis, a diploid perennial teosinte. This plant is fertile, has proven to be cross compatible with Zea mays L. and offers an avenue to expand the gene pool for commercial corn varieties. The instant plant is perennial, offers resistance to corn rootworm, remarkable drought tolerance, and prolific production of fruit.

BACKGROUND OF THE NEW PLANT

Two wild grasses, perennial teosinte, Zea diploperennis Iltis, Doebley and Guzman, and Eastern gamagrass, Tripsacum dactyloides L. have been crossed to produce a fully fertile bridge species that may improve corn, Zea mays L., by conferring beneficial traits such as pest resistance and drought tolerance. Z. diploperennis (hereafter referred to as diploperennis), was an unkown wild relative of corn until it was discovered, apparently on the threshold of extinction, in the mountains of Jalisco, Mexico in the late 1970's. It is in the same genus as corn, has the same chromosome number as corn (n=10), and hybridizes easily with it. Gamagrass is a more distant relative of corn with a different haploid chromosome number (n=18), and varying ploidy levels ranging from 2n=36 to 2n=108. Tripsacum has been crossed with corn by artificial techniques and hybrids obtained are male sterile and essentially female sterile. All attempts to cross Tripsacum and annual teosinte, the closest relative of corn that some scientists believe is its wild progenitor, failed. Many plant breeders believe that Tripsacum has significant potential for improving corn by expanding its genetic diversity.

In 1984, crosses were made by pollinating diploperennis with pollen from a tetraploid (2n=72) T. dactyloides. U.S. Plant Pat. No. 6,906 for Sun Dance, the hybrid from that cross, was issued Jul. 4, 1989. In April, 1985, the reciprocal cross to the tetraploid Tripsacum was made using diploperennis pollen, and U.S. Plant Pat. No. 7,977 for Tripsacorn, the hybrid from that cross, was issued Sep. 15, 1992. U.S. Pat. No. 5,330,547, a utility patent on the method for transferring Tripsacum nuclear and cytoplasmic genes into maize via Tripsacorn, was issued Jul. 19, 1994. Ser. No. 08/248,333, filed May 24, 1994, is a continuation of the utility patent involving hybrid material, derived from a Tripsacum female parent pollinated by diploperennis, in crosses to maize.

On Jan. 18, 1988, pistillate inflourescences on a diploperennis plant were pollinated with pollen from a distinctly different T. dactyloides that is a diploid (2n-36) rather than a tetraploid plant. The seed was harvested and stored until Jan. 18, 1992, when it was germinated. The seed had been stored for four years because it was pale in color and did not appear viable. Earlier attempts to germinate seed obtained from crossing diploperennis and Tripsacum plants that were not tetraploid had failed. The reason I attempted to germinate the seed in 1992 was I decided to cull all old seed from earlier crosses. As a precaution, I never throw out seed until I run it through a standard germination test. Much to my surprise a single seed from this cross germinated and grew to produce a normal, fully fertile plant that is perennial and produces viable fruits twice annually.

Sun Star has been propagated by rhizome divisions and cuttings. Crosses have been made to inbred corn line W64A. Sun Star is similar to Sun Dance and Tripsacorn, hybrids derived from crossing tetraploid Tripsacum with diploperennis, in that it is fertile and cross-fertile with corn. It provides another novel genetic bridge for moving genes from a different Tripsacum into corn, thereby establishing a link between these wild grasses and modern corn that may be beneficial in corn improvement breeding programs.

Sun Star is distinctly different from Sun Dance and Tripsacorn in that its Tripsacum parent is a diploid rather than a tetraploid and comes from a different geographical area than the tetraploid Tripsacum plants. Therefore, previously patented plants are not intimately related to the invention of this material which used a parent plant with different qualifications. Unique propagation of Sun Star through successive generations by means of cuttings has demonstrated that the new plant has not only retained the continuous and abundant production capability, but also that its distinguishing characteristics hold true from generation to generation and appear to be firmly fixed. Propagation has taken place in Durham, N.C.

In bioassays, Sun Star shows distinct resistance to the larvae of Western corn rootworm, Diabrotica virgifera, as indicated by no root feeding damage and no larvae retrieved. In a field test during August, 1995, after the plant went without water for a week with temperatures exceeding 90° F. during the day, Sun Star was still green and appeared as though it had been watered; whereas, under the same conditions, Tripsacorn, Sun Dance and diploperennis suffered severe wilting and most of the vegetative growth turned brown and died. In addition to corn improvement, other obvious utility for Sun Star includes potential as a perennial forage crop on marginal land, use as a ground cover, and prolific production of novel grain.

DESCRIPTION OF ILLUSTRATIONS

This new plant is illustrated by the accompanying full color photographs which show

(1) a fully grown plant showing the characteristic habit of many culms growing from the base,

(2) a closeup of the culm showing red speckles, a characteristic that resembles the purple blotched effect of the pl₁ gene in corn, and the open sheath that does not completely enwrap the culm, a characteristic unique to Sun Star,

(3) a close-up of aerial roots at a node along the culm,

(4) a close-up of a leaf showing the white midrib and parallel veins,

(5) a close-up of two pistillate spikes with long pilose styles showing the distichous arrangement of developing caryopses, and

(6) a close-up shoeing multiple pistillate spikes borne at a single node, several are pedicellate and one is sessile.

THE PLANT

Origin: Seedling.

Parentage:

Seed parent.--Zea diploperennis (2n=20). Source: Jalisco, Mexico, R. Guzman M. Acc. #777.

Pollen parent.--Tripsacum dactyloides (2n=36). Source: K. Anderson, Manhattan, Kans.

Classification:

Botanic.--Zea indiana (proposed).

Chromosome number: 2n=20

Habit: Essentially erect; as many as 25 primary culms, usual number about 10.

Duration:

Perennial.--Sends out shoots from rhizomes. Plants will freeze at winter temperatures below 28° F., but new growth is produced in spring after winter temperatures of 0° F.

Culm:

Height.--Up to 1.7 meters: slender, simple with occasional branching from the nodes of the culm; glabrous; oval in cross section; diameter 1.5 cm.

Nodes.--Glabrous; around 12 per culm; length between nodes 10.0 cm; aerial roots develop at nodes along culm.

Sheath.--Not tightly closed enwrapping the culm as is typical of most Zea species, margins not united; glabrous; red speckles (Pantone #18-1860), otherwise green.

Ligule.--Present on adaxial side of leaf at junction of blade and sheath; length: 3.8 mm; membranaceous, irregular edge.

Leaf blade: Alternate; distichous; sheathing base; parallel veined; narrowly linear, flat, thin.

Length.--60 cm.

Width.--3.1 cm.

Entire margin.--Serrulate, white (Pantone #12-5202).

Midrib.--White (Pantone #12-5202).

Adaxial surface.--Hispid.

Abaxial surface.--Hispidulous.

Prominent parallel veins.--5 per 1 cm width.

INFLORESCENCE

Blooming period: Twice annually for approximately 6 weeks beginning in late September and April in North Carolina.

Monoecious: Separate male and female flowers on same plant.

Staminate flowers: May be of two types: one inflorescence type borne as paired spikelets on a slender rachis forming 7 to 37 racemes arranged in a panicle, the "tassel", at the summit of the culm. The anthers emerge and shed pollen before the styles of the pistillate spikes appear. Alternatively, staminate spikelets may be borne on a single spike above the pistillate flowers, in which case pollen shed coincides with appearance of pistillate styles on the same spike.

Length.--19 cm.

Axis.--Stiff, continuous, ascending.

Spikelet: Two-flowered, one sessile, one pedicellate; laterally compressed awnless.

Length.--9.5 mm.

Width.--2.6 mm. In pairs on one side of a persistent central hirsute axis.

Pedicel length.--4.5 mm.

Glumes.--Outer glume: cartilaginous, tapering to an acute tip, ciliate, flat, several nerved, margins scabrous. Inner glume: chartaceous.

Anther.--Length: 4 mm, Width: 1 mm. Color at maturity caramel (Pantone #16-1439).

Pollen viability: 98%.

Pistillate flowers: Borne in leaf axils; three or more pistillate spikelets per node, one sessile and others pedicellate; pedicel length: 1-2 cm; spikelets distichously arranged; pistillate flower consists of a single rowed spike of 6 to 10 trapezoidal caryopses in hard, shell-like fruitcases; most enclosed in a single leaf sheath, but some not enclosed; caryopses disarticulate upon maturity. Production of pistillate flowers follows anthesis of staminate flowers.

Styles.--Pilose.

Color.--Ranges from pastel parchment (Pantone #11-0603) to light lilac (Pantone #12-2903) to rose red (Pantone #18-1852) to burgundy (Pantone #19-1617).

Length.--80 mm.

Fruit: As many as 40 ears per culm per blooming period; flowers produced twice a year; under ideal conditions, some plants may produce over 800 ears twice annually.

Maturity: 45 days following fertilization.

Color: Most kernels are dark earth (Pantone #19-1020) with shadings of tobacco brown (Pantone #17-1327) and cashew (Pantone #17-1137). Others are sheepskin (Pantone #14-1122) to gray sand (Pantone #13-1010) with dark speckles (Pantone #19-1020 or Pantone #17-1137) and others are two-toned with a pale hardened outer glume (Pantone #14-1122) and a dark hardened inner glume (Pantone #19-1020).

Kernel (dried): Angular caryopses in hard, shell-like fruitcases, disarticulate upon maturity:

Size: Length about 6.5 mm, Width about 4.0 mm, Thickness about 3.3 mm.

Shape: Trapezoidal.

Weight: 20 seed (unsized samples): 1.2 g.

COMPARATIVE PARENTAL CHARACTERISTICS

Selected phenotypic traits of both parental species are described below, and compared to Sun Star in Table 1.

Culm: Zea diploperennis round in cross section; diam. 1 cm; sheath tightly closed completely enwrapping the culm; Tripsacum dactyloides oval in cross section; diam. 1.3 cm; sheath splits apart and does not enwrap the culm.

Leaf blade:

Z. diploperennis.--Length: 77.5 cm. Width: 5.0 cm; margins pink serrulate from midsection of blade to tip; adaxial surface: hirsutullous; prominent veins: 6 per 1 cm width.

T. dactyloides.--Length: 105 cm. Width: 2 cm; margins white serrulate along entire blade; Adaxial surface: hirsutullous; prominent veins: 8 per 1 cm width.

Blooming period: Z. diploperinis twice a year, end of March and end of September for about a month. T. dactyloides continuously from May to October.

Staminate flowers: Z. diploperennis borne in tassel at summit of culm. T. dactyloides staminate flowers borne above pistillate flowers on single spike.

Pistillate flowers: Z. diploperennis caryopsis triangular in hard bony fruitcases; Length: 8 mm; Width: 4.5 mm; Color: black (Pantone #10-0303), dark brown (Pantone #10-1020) or brown speckled. T. dactyloides caryopsis trapezoidal in hard, bony fruitcase; Length: 8.5 mm; Width: 6.5 mm. Color: pale brown (Pantone #17-1137) or buff (Pantone #13-1024).

Color reference: Leatrice Eiseman and Lawrence Herbert, The Pantone Book of Color. Harry N. Abrams, Publishers, New York, 1990.

                  TABLE 1                                                          ______________________________________                                         Comparison of Sun Star Traits with Parental Species                                   Sun Star  Diploperennis                                                                              Tripsacum                                         ______________________________________                                         Culm                                                                           Cross section                                                                           Round       Round       Oval                                          Diameter 1.5 cm      1.8 cm      1.3 cm                                        Sheath   split       overlapping split                                         Leaf blade                                                                     Length   60.0 cm     77.5 cm     105.0 cm                                      Width    3.1 cm      5.0 cm      2.0 cm                                        Margins  white serrulate                                                                            pink serrulate                                                                             white serrulate                               Adaxial  hispid      sparsely hirsute                                                                           scabrous                                      surface                                                                        Veins    5/cm        6/cm        8/cm                                          Blooming twice annually                                                                             twice annually                                                                             May-Oct.                                      period   6 wks. late 4 wks. late                                                        Sept., Apr. March, late                                                                    Sept.                                                     Staminate                                                                               in tassel or                                                                               in tassel   above pistillate                              flowers  borne above             flowers on same                                        pistillate              spike                                                  flowers on same                                                                spike                                                                 Pistillate                                                                     flowers                                                                        Caryopsis                                                                               trapezoidal triangular- trapezoidal                                   shape                trapezoidal                                               Fruitcase                                                                               7 mm        8 mm        6-10 mm                                       length                                                                         Fruitcase                                                                               5 mm        4-5 mm      6 mm                                          width                                                                          Color    dark brown to                                                                              black, dark beige                                                  beige; speckled                                                                            brown                                                              to two-tone                                                           ______________________________________                                    

COMPARISON TO SUN DANCE AND TRIPSACORN

Although Sun Star is similar to Sun Dance and Tripsacorn, it is distinctive from these plants because it was derived from pollinating a Z. diploperennis seed parent with a diploid T. dactyloides (2n=36); whereas the other two crosses used a tetraploid T. dactyloides (2n=72). It is distinguished from Sun Dance by its strong resistance to corn rootworm. It is different from both plants in that it produces only one type of pistillate inflorescence on a single spike, greater numbers of ears at each node, is much more prolific in seed production than Sun Dance or Tripsacorn, and has much greater tolerance to drought and heat than Sun Dance and Tripsacorn. Annother characteristic difference from the other two hybrids is that the sheath is split as in its Tripsacum parent, rather than tightly enclosed around the culm. Also, Sun Star has greater fertility than the other two hybrids, as indicated by its 98% pollen viability compared to Sun Dance and Tripsacorn which are 92% and 94%, respectively. Certain Sun Star traits summarized comparatively with Sun Dance and Tripsacorn in Table 2.

                  TABLE 2                                                          ______________________________________                                         Comparison of Sun Star with Sun Dance and Tripsacorn.                                 Sun Star  Sun Dance   Tripsacorn                                        ______________________________________                                         Parentage                                                                      Seed parent                                                                             Z. diploperennis                                                                           Z. diploperennis                                                                           T. dactyloides                                Chromosome                                                                              2n = 20     2n = 20     2n = 72                                       no.                                                                            Origin   Jalisco, Acc.                                                                              Jalisco, Acc.                                                                              Santa Claus, IN                                        #777        #777                                                      Pollen parent                                                                           T. dactyloides                                                                             T. dactyloides                                                                             Z. diploperennis                              Chromosome                                                                              2n = 36     2n = 72     2n = 20                                       no.                                                                            Origin   Manhattan, KS                                                                              Santa Claus, IN                                                                            Jalisco, Acc.                                                                  #1250                                         Culm                                                                           Height   1.7 m       2.0 m       2.0 m                                         Number   up to 25    up to 15    up to 35                                      Diameter 1.6 cm      1.5         1.2                                           Ears/culm                                                                               5-40        5-10        5-10                                          Sheath   split       overlapping overlapping                                   Cross section                                                                           oval        oval        oval                                          Diameter 1.5 cm      1.5         1.2                                           Leaf Blade                                                                     Avg width                                                                               3.1         3.3         3.3                                           Avg length                                                                              60 cm       52 cm       52                                            Margins  white serrulate                                                                            red serrulate                                                                              red serrulate                                 Adaxial  hispid      sparsely hirsute                                                                           sparsely hirsute                              surface                                                                        Veins    5/cm        4/cm        5/cm                                          Blooming twice annually                                                                             twice annually                                                                             twice annually                                period   6 wks late  4 wks late Oct.,                                                                           4 wks late Oct.,                                       Sept., Apr. late Apr.   late Apr.                                     Staminate                                                                               in tassel or                                                                               in tassel or                                                                               in tassel or                                  flowers  borne above borne above borne above                                            pistillate  pistillate  pistillate                                             flowers on same                                                                            flowers on same                                                                            flowers on same                                        spike       spike       spike                                         Spikelet 9.5 mm      9.0 mm      11.0 mm                                       length                                                                         Spikelet 2.6 mm      2.0 mm      3.0 mm                                        width                                                                          Pedicel  4.5 mm      5.0 mm      3.0 mm                                        length                                                                         Pollen   98%         92%         94%                                           viability                                                                      Pistillate                                                                     flowers                                                                        Style    pink to     pink to red,                                                                               pink to red,                                           burgundy,   pilose      pilose                                                 pilose                                                                Style length                                                                            80 mm       65 mm       100 mm                                        Caryopsis                                                                               trapezoidal triangular  triangular                                    shape                                                                          Kernels per                                                                             6-10        4-6         4-6                                           spike                                                                          Fruitcase                                                                               6.5 mm      7.0 mm      5.0 mm                                        length                                                                         Fruitcase                                                                               4.0 mm      5.0 mm      5.0 mm                                        width                                                                          Color    dark brown to                                                                              pale with   dark brown to                                          beige; solid,                                                                              brown speckles                                                                             beige; solid or                                        speckled or             speckled                                               two-tone                                                              ______________________________________                                     

I claim:
 1. A new and distinct variety of corn plant, substantially as herein shown and described characterized by its profuse production of fruit, perennial habit, resistance to corn rootworm, and strong tolerance to drought and high temperatures. 